Achieving an airtight seal at all of the exhaust system's various connections is important in maintaining your vehicle's performance and reliability. Exhaust leaks create turbulence in the exhaust gas flow, robbing your engine of horsepower. Exhaust leaks can also lead to various malfunctions of the engine's emissions system. Aside from these technical complications, exhaust leaks will often give your car a loud, raspy exhaust note. Replacing all exhaust gaskets with new units and properly tightening all exhaust flange connections will ensure your exhaust system is sealed properly.
Use a floor jack to raise the side of your vehicle where the exhaust system is installed. For user safety while working under the vehicle, support the chassis on jack stands.
Remove the exhaust flange bolts at each end of the exhaust segment from which the exhaust leak is originating. The exhaust's catalytic converters, cat-back piping, and mufflers are constructed in multiple segments. Each segment is connected to the next via two bolts secured into an exhaust flange. There are also metal hangers attached to various exhaust segments which secure to the underside of the vehicle with rubber connecters. After unbolting the exhaust segment you wish to remove, slip the rubber hanger free from its connection on the underside of the vehicle, and work the exhaust segment free from the rest of the system.
Install new exhaust gaskets onto each end of the exhaust segment you removed. Even if only one of the flange connections was leaking, you should replace both gaskets with new units, as reusing crushed exhaust gaskets will increase the risk of a future leak developing. You may also want to try coating the exhaust bolt threads with a thread-locking liquid, as this will help ensure the exhaust bolts don't work loose over time.
Fit the exhaust segment back into the exhaust system, taking care not to damage the exhaust gaskets. Re-install the exhaust flange bolts. Use a large socket wrench when tightening the flange bolts, as this will give you increased leverage, allowing you to get the bolts extremely tight. This will help seal the gaskets and ensure the exhaust flange doesn't gradually loosen.